1. Field of the Invention
The present invention relates to a communication scheme for carrying out voice (speech) or data communications through a radio telephone network, and more particularly to a communication scheme in which a connection to the Internet is made via a radio telephone network and voice or data communications are carried out in the IP packet format through this connection.
2. Description of the Background Art
Due to the spread of portable telephone (cellular telephone) or PHS (Personal Handyphone System) terminals, communication services utilizing the radio communication system are now widely in use. In these portable telephone (cellular telephone) or PHS terminals, communication services are realized by carrying out radio communications with radio base stations and being multiply connected to wired communication networks through these base stations.
On the other hand, due to the spread of the worldwide computer network called the Internet, various information services on the Internet have been developed. In particular, much attentions have been attracted to the Internet telephone (IP telephone) for carrying out communications through the Internet by assembling IP packets from telephone voice data, which takes the advantage of the fact that communication cost is quite low on the Internet compared with the conventional telephone network. Typically, as shown in FIG. 19, IP telephone gateways for relaying between a voice telephone network and the Internet are provided inside telephone stations, for example, and communications between these gateways are realized through the Internet such that communications can be carried out with only a fee up to the closest telephone station (or the closest IP telephone gateway location) even in the case of long distance telecommunications.
Such an Internet telephone is also applicable to the case where the terminal is a radio portable terminal such as a cellular telephone or PHS terminal. For example, as shown in FIG. 20, the Internet radio telecommunication system can be realized by providing a router device for managing a plurality of radio base stations such that this router device functions as the IP telephone gateway and carries out data exchange with the Internet.
Of course, on the Internet, multimedia data in various formats can be transferred according to the standard protocol. For example, voice, still images, dynamic images, data files of specific application, etc. can be transferred by the single TCP/IP protocol by assembling IP packets from these data. Consequently, in FIG. 20, by setting up a protocol for transferring TCP/IP packets between the router device and the radio portable terminal through the radio base station, it becomes possible to exchange these multimedia data transferred on the Internet while utilizing the Internet telephone at the same time. More specifically, it becomes possible to realize an application which enables voice communications while transferring related image data (data of references or maps, for example), or receiving a news clip in voice while also receiving related photographs as images.
However, in the case of carrying out the multimedia communications including the Internet telephone as described above by using a radio portable terminal, the radio portable terminal which generally has a compact size is expected to be associated with various limitations regarding resources.
For instance, there can be cases where even when the image data are received, there is no display device that can display the received image data in sufficient resolution. There is also a limitation that the screen size is small.
Also, because the multimedia data generally have large data sizes, it is even possible to encounter situations where the entire transmitted multimedia data cannot be stored in the worst case.
On the other hand, in view of the environment in which the Internet and the telephone network are utilized, in many cases the utilization environment of the radio portable terminal is generally worse compared with the ordinary fixed PC, for example. For instance, there can be cases where a contract for the local telephone can be made at a fixed rate only for the fixed PC at one's home but not for the radio portable terminal, or cases where many Internet applications are more convenient to use on the ordinary PC than the radio portable terminal (such as cases where many more Web address information can be maintained on the ordinary PC than the radio portable terminal for obvious reasons).
As described, in the case of realizing an Internet service that handles the Internet telephone and the multimedia data by using a radio portable terminal, the radio portable terminal which generally has a compact size is associated with many limitations regarding resources, such as a lack of a display device capable of displaying image data in sufficient resolution, or a lack of ability for mounting a storage device such as memory or disk that can store the large amount of multimedia data, for example.
Also, the radio portable terminal is associated with a poorer handling of applications or a poorer environment that requires a higher communication medium utilization fee, for example, compared with the fixed PC at a home or even the portable note PC.